Hold your horses here. The "Disciples of Christ" are NOT "mainline Christians". I have never even heard of them until now. This is like attaching Phelps (of the godhatesfags.com) to the Southern Baptist just because he calls his church "Baptist".
Even though you're probably right about this particular denomination not representing most, I still stand by my remarks. You might want to check out the National Council of Churches web site.
Try Alexander Campbell. You can even look up early Mormon history (if that makes you more comfortable) and run into these guys ~ one branch of the early DoC ran off with Smith and Young in fact.
The Christian Church Movement is an outgrowth of the Restoration movement (not to be confused with the Reconstructionist movement).
Although DoC usually runs from 1.5 to 2.0 million in estimated membership (which counts ONLY baptised adults), the closely related independent Christian Church has about that many, and the Church of Christ (non-instrumental), theologically identical and sharing the same origins, but they sing a capala in the round, has more.
All told there are well over 10 million people (adults, children) who have some affiliation with one of these churches ~ however, ONLY the DoC makes resolutions.
As an item of interest, some members of the Christian Church (any of the three major divisions) believe adornment in the form of hats or jewelry constitutes idolotry. This is sometimes viewed as antisemitic by Jews who are shocked if a member of one of these churches refuses to don a yarmulka at a Jewish event. It's not antisemitic ~ and these guys don't necessarily bow their heads at prayer, and would probably have a full blow-out if required to kneel at an altar railing. I can only imagine what would happen to them in the presence of a Shi'ite going through the "let's pretend" handwashing before prayers. And the Pope? Can you see the reaction to a papal crown? My word! Shock, I tell you, shock ~ that's what they'd feel.